A response to Jack's comments on the Economist charts.
Junk Charts pleads guilty to the charge that this blog's attitude is seriously serious, except on rare occasions. That is because we believe data analysis to be a serious subject. That said, we do wonder how entertainment value can co-exist with data integrity; and thus far, we have not found the happy medium.
Tufte's favorite chart of Napoleon's Russian campaign is one example of an entertaining and informative chart. For anyone who knows or follows the Bumps Race, the Bumps chart is highly expressive. We believe that entertainment can be a by-product og graph-making but deliberately seeking it is folly.
Case in point: the palm-tree hedge-fund plot Jack thought to be funny.
At the least, when adding entertainment, the designer must be careful not to distort the data contents but even minor chartjunk can insidiously ruin an otherwise competent chart, as happened here.
Getting rid of the chartjunk, we would revert to a standard time-series chart on a rectangular grid. The palm-tree axis, being curved, is a curious little feature. Its presence meant that the rectangular grid interpretation no longer applies! When reading the data for 2000 for instance, one must trace a curved lines upwards, not the usual vertical line.
The right chart illustrates this. If the designer switches to a curved grid, then the trend line must be transformed from the black line to the red line. (This may remind some of Jacobian transformations in multi-variable calculus.) The error in the Economist chart is akin to showing the black trend line on the red grid.
Also, when the designer focuses on beautifying the chart, she may become careless. For instance, why on earth should the vertical axis start at negative $25 billion assets? One would think that hedge funds with negative assets do not, and cannot, exist. Perhaps it's truly "far from expected" in the Caymans!
I encourage other readers to comment if they have ideas as to how to integrate entertainment into data graphics.